Molecular intactness of transferrin recycled in a myogenic chicken cell culture

Evidence has been accumulating that transferrin (Tf), an iron-binding glycoprotein, is a unique ligand in that it is recycled intact. We examined the properties of chicken Tf molecules recycled in a myogenic chicken cell culture. No difference in the isoelectric focusing pattern before and after recycling, nor any marked change in the total Tf concentration in the culture medium was found during culture. And, although recycled Tf had no myotrophic activity in vitro, it regained its original activity when reloaded with iron. These results are evidence of the molecular intactness of recycled Tf.